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HPM-2002-OBEVacuum Gauge Page 13 of 39
3.2. Analog Output (4-20mA)
The HPM-2002-OBE with analog output and display is shown in the figure below. The user interface
consists of a status bar, a mode bar, and setpoint test jacks.
3.2.1. Overall Functional Description
The status bar gives information about the condition of the HPM-2002-OBE. High and Low indicate
whether the set points are activated. Error indicates if there was a problem downloading the EEPROM. Torr
and mTorr indicate what pressure regime the gauge is measuring.
The mode bar indicates which mode has been selected. The HPM-2002-OBE has five modes which the
user may enter. This is similar to the six modes which can be entered in the bench top/panel mounted HPM-
2002, there is no interlock feature; when the user changes the settings within a mode any adjustments that have
been made will be permanent once the mode is exited. (To exit without making changes permanent, the user
must turn the power off.)
3.2.2. High and Low Set Point Modes
The HPM-2002-OBE provides TTL outputs for process control. These signals are available on the 15-pin
connector (see previous table in Section 2.4).
To view the High set point, place the HPM-2002-OBE in the High mode by pressing the SELECT button
until the High mode light is illuminated. The display then shows the set point selected. During normal operation
the alarm light will illuminate and the TTL output (pin # 1) will go high (+5V) if the pressure exceeds the set
point.
Similarly, to view the Low set point, place the HPM-2002-OBE in the Low mode by pressing the SELECT
button until the Low mode light is illuminated. The display then shows the set point selected. During normal
operation the alarm light will illuminate and the TTL output (pin # 2) will go high (+5V) if the pressure
becomes less than the set point.
To adjust a setpoint, place the HPM-2002-OBE in either setpoint mode (High or Low). Next, use the
ADJUST rotary encoder until the desired setpoint is displayed. Finally, place the HPM-2002-OBE back in the
Run mode. The new set points are now stored in the HPM-2002-OBE’s memory.
3.2.3. Run Mode
The HPM-2002-OBE will automatically enter the Run mode upon start-up. This is the mode for normal
operation and the mode in which the instrument will spend most of its time. In the Run mode the HPM-2002-